1. Field of the Invention
This invention in general relates to buzzers of the type in which a striking member is excited by an electromagnet and a vibration diaphram is struck by the excited striking member thereby producing an audible signal.
Generally speaking, the present invention includes means for improving the electroacoustical properties of a buzzer as described above which attenuates undesirable frequencies of the audible signal thereby producing a predominant signal frequency and accentuates the predominant frequency by utilizing a resonant chamber having a resonant frequency substantially equal to the predominant frequency of the audible signal.
2. Description of the Prior Art
In a conventional buzzer of the type which includes a striking member and means for vibrating the striking member an audible signal is generally produced by the vibrating striking member striking some type of a vibration diaphram. Typically, the striking of a vibration diaphram comprised of a metal, such as is taught in U.S. Pat. No. 3,760,411 has resulted in a complex series of vibrational modes containing a wide spectrum of frequencies which produces an unpleasant audible signal. As exemplified by U.S. Pat. No. 3,564,542, efforts have been made to improve the electroacoustical properties of the conventional electromechanical vibrating buzzer. These efforts have included the use of a vibration diaphram comprised of a plastic film and/or the shaping of either plastic or metal vibration diaphrams to accentuate the acoustic response of the buzzer. While these improvements have produced buzzers with improved electroacoustical qualities, it is in many instances desirable to reduce the "noise" factor associated with such buzzers to obtain an audible signal which is even less irritating and more aesthetically pleasing. A typical instance where a more aesthetically pleasing audible signal is desired is the use of such buzzers in automobiles to signal either that a safety belt is unfastened or that keys have been left in the ignition when the driver leaves the automobile.